The present invention relates to a covering for a ground opening, comprising a frame and a cover inserted and supported in the frame. The outer circumferential support surface of the cover and the inner bearing surface of the frame are constructed as corresponding, cooperating surfaces inclined towards the cover plane.
Coverings are used for closing a ground opening, e.g. a shaft opening in a ceiling, and if necessary can be opened without difficulty. Such coverings are known in various different constructional forms. The cover can be rectangular, oval, or circular, whereas the frame generally has a rectangular outer contour, independently of the cover shape. It is required in certan cases for the cover to form a tight termination of the ground opening. In order to satisfy this requirement, known solutions make use of relatively soft rubber packings or a rubber-elastic plastic. Although this leads to a good seal, problems occur if the packing is damaged or displaced on opening, so that during the subsequent closing of the ground opening the necessary sealing action is no longer ensured.
EP 0 142 160 discloses a sealing arrangement for sealing a cover on the bearing surface of the associated frame, in which the aforementioned deficiencies do not occur. The cover can have support surfaces inclined with respect to the cover plane. These surfaces cooperate with corresponding bearing surfaces of the frame. A circular recess is made in the support surface or the bearing surface and this is filled with a sealing compound. If the cover is carefully opened and reinserted, the sealing action is completely maintained. However, if the cover is not carefully removed, the complete sealing is not ensured. It may be necessary to press some sealing compound into the recess and for this purpose there are corresponding openings in the cover of the frame.
The use of the known sealing means is particularly appropriate in the case of covers and frames, whose support surfaces and bearing surfaces are inclined towards the cover plane. If the cover is rectangular, a satisfatory seating of the cover in the frame is ensured. However, if the cover is circular, it is necessary to make use of soft packings and to screw the cover onto the frame, accompanied by the compression of the packing. Thus, when opening such a cover, the aforementioned problems can occur.